Sealing-in method and apparatus



Nov. 21, 1950 R. H. STUART 2,531,008

SEALING-IN METHOD AND APPARATUS Filed April 14, 1944 I: m ,9 E 9 M E ,2 E i 444 E /0 I'nventor: Raymond H. SCuarc,

Hi5 Atforneg.

Patented Nov. 21, 1950 SEALING-IN 'METHOD AND APPARATUS Raymond vH. Stuart, Cleveland, Ohio, assignor to General Electric Company, a corporation of New York Application April .14, 1944, Serial No. 530,952

3 Claims.

.My invention relates in general to methodand apparatus for the manufacture of tubular fluorescent lamps, and in particular to an improvement in method and apparatus for sealing the mounts to the opposite-ends of such lamps.

.In the manufacture of fluorescent lamps of the well-known type in commercial use at present, it is-customary to first apply the coating of fluorescent material to the internal wall of the lamp onvelopeafter which the lampmounts are sealed to the opposite ends of the envelope. Thesealing-in of the lamp mounts is usually accomplished by supporting the tubular lamp envelope in a vertical position with its lower end resting on the glass flare of the mount, and then suitably heating the glass of the envelope and flare, at and adjacent the junction therebetween, to thereby fuse and seal the parts together. 7

.Onemethod of heating the glass parts to ef feet the fusion and sealing thereof is by the use of gas fires. directed across the adjoining glass surfaces, asdisclosed in US. Patent No. 2,434,664, F. J. lvlalloy, issued January 20, 1948. However, because of the slight space or gap w'hich frequently exists between the lower end of theenvelope and the flare of the mount and which is due to the absence of. perfectly true or square ends on the envelope, the use of gas sealing-in fires will :result in the formation of unsightly and undesirable discoloration bands in the fluorescent coating on the lamp envelopes whenever the upper end of the envelope is open to the atmosphere duringthe sealing-'in-operation. .Such-discoloration bands are formed by the condensation of the-water paper which is "usually present in the gaseous combustion mixture employed for the gas sealing-in fires'and which is directed by the gas burners into the envelope through the aforementioned space or gap between the lower end of the envelope :and the flare of the mount. Upon entering the envelope, the water vapor is then--.carried upwardly therethrough by the upward draft or gas current which formsin the upwardly open envelope during the heating operaticns, the tubular envelope serving inefiect as a chimney forproducing the updraft. Uponreaching the cooler upper wall surfaces of the envelope, the water vapor condenses on the inner wall-of the envelope and is absorbed by the fluorescent powder particles thereon, thereby discoloring the said particlesandso forming the discoloration bands referred to previously.

One object of my invention is to provide an improvement .in the gas-fire sealing-in method for sealing the mounts to the endsuof tubular fluorescent lamp envelopes which will obviate the formation of discoloration bands in the linorescent coating on the inner wall of the envelope. Another object of my invention is to provide improved gas-fire sealing-in apparatus for tubular fluorescent lamp manufacture.

Further objects and advantages of inven tion will appear from the folowing description of a species thereof and from the accompanying drawing in which:

Fig. 1 is a somewhat diagrammatic plan View of a sealing machine comprising my invention; Fig. 2 is avertical section through one of the heads of the machine located at one of the gasfire heating stations; and Fig. 3 is an enlarged fragmentary section through one of the head spindles, with -a lamp-envelope and mount shown in proper sealing position thereon.

In accordance with the invention, the formation of moisture discoloration bands on the inner wall of the lamp envelope is effectively eliminated by preventing the water apor in the gasfire combustion mixture from coming in contact with portions of the envelope wall which-are sunlciently cool to cause the water vapor to condense thereon. This is preferably accomplished by directing a stream of dry or moisture-free air or gas, at a suitable pressure, downwardly through the envelope during the gas-fire heating operations. The pressure of the air or gas so introduced into the envelope should be suificient to at least overcome the upward draft through the envelope and create a slight outward flow of air or gas through any space that may exist between the lower end of the envelope and the flare of the stem.

Referringto thedrawing, the invention is there shown as applied to a fluorescent lamp mount sealing-in machine of the gas-fire type disclosed and claimed in the previously mentioned U. S. Patent No. 2,434,664 of F. J. Malloy. The said machine comprises, in general, a turret l provided with a plurality (16) of heads 2 located at uniformly spaced'intervas around. the periphery of the turret. The turret is supported on a vertical shaft 3. journaled in the machine bed (not shown) and is intermittently rotated in a counterclockwise direction to successively index or advance the heads 2 to a plurality of work stations A to Q corresponding in number to the number of heads. The indexing means for the turret i may be of any well-known type, such as that illustrated in U. S. Patent No. 1,742,153, Stiles etaL, andcomprising a rotating drum-type earn t mounted on a horizontal drive shaft '5. and

envelope 9 in proper sealing relation to one another with the envelope disposed vertically and its lower end resting on the flare of the mount stem. The mount 8 illustrated in the drawing is of the type shown in U. S. Patent 2,312,245, J. Flaws, and comprises a glass stem I having a flare portion I I, and a pair of leading-in wires I2 sealed through the stem and connected at their near ends to a filamentary coil electrode I3 coated with a suitable electron emissive material, such as an alkaline earth oxide, like barium oxide, for instance.

Each of the heads 2 comprises a vertical spindle M rotatably mounted in roller bearing I5 supported in housings I6 on the turret I. The spindle I4 is provided with an upwardly projecting mount support pin I! having a flange or head I8 at its upper end on which the mount 8 is adapted to rest in an upright position, as shown in Fig. 3. The pin I! is provided with an axial opening I9 to accommodate the exhaust tube 29 and the leading-in wires I2 of the mount 8. To facilitate the centering of the mount 8 on the top of the pin I1, the flange I8 of the pin is provided with a conical upper surface 2| conforming more or less to the conical shape of the flare portion II of the stem I0.

Each head 2 is also provided with a suitable holder 22 for supporting the tubular lamp envelope 9 in a vertical position in alignment with, and resting on the flare II of the mount 8 on pin I1. The holder 22 is fastened to a vertical column or post 23 extending upwardly from and secured to a flange 24 on the spindle I l.

The operation of the machine is generally similar to that described in the previously mentioned U. S. Patent No. 2,434,664, the mount 8 and the envelope 9 being first loaded into the head 2 at the loading stations A and B after which the turret indexes the head through idle station C and thence through a series of successive heating stations D to O inclusive where the stem flare II and the lower end of the envelope 9 are heated by gas fires 25, 26 or 2'! at each of said stations (the fires not being shown at stations G to N) to thereby fuse and seal the glass parts together. After it has passed through a cooling station P, the sealed envelope and mount are then removed from the head 2 at the unloading station Q.

To insure the heating and sealing together of the glass parts uniformly around their periphery, the heads 2 are continuously rotated during the interval when they are positioned at each of the said heating stations D to O inclusive. Such rotation of the heads 2 may b eifected in any suitable manner, such as by the chain-belt and sprocket arrangement shown in the aforesaid U. S. Patent No. 2,434,664 wherein a moving chain-belt engages with and rotates a sprocket on the head spindle Id.

The gas fires 25 at the first two heating stations D and E are in the form of soft flames which merely serve to preheat the glass parts, while the gas fires 26 at the following stations F to N are very sharp and hard, and serve to produce the actual fusion and sealing together of the flare I I and the end of the envelope 9. The actual union or seal between the glass parts is first formed just after the head 2 begins to index away from the fourth sealing-fire station J, at which time 4 the mount support pin I1 is given a sudden slight upward movement to upset the softened rim of the glass flare II and press it into firm and intimate contact with the softened lower end of the envelope 9. The sealing fires at the following stations K to N (corresponding to fires 26 shown at station F) are used to further form and shape the seal and complete the same, while the gas fires 21 at station 0 are used to anneal the glass seal to thereby minimize the internal strains therein.

In accordance with the invention, jets of compressed dry air 28 are directed downwardly through the envelope 9 at each of the gas-fire heating stations preceding that position in the rotary travel of the envelope and flare around the machine where they first become actually united or sealed together, the air being at a pressure suflficient to overcome the updraft that tends to form within the envelope because of the chimney eifect thereof, and preferably producing a slight downward flow of air through the envelope and out through any gap that may exist between the lower end of the envelope and the flare II of the stem [0. Such outward flow of air through the gap between the envelope and the flare thus prevents the water vapor in the gas heating fires and 26 from passing through the said gap and into the envelope where it would then have an opportunity to ascend and condense on the inner wall of the envelope to thereby form the moisture discoloration bands previously referred to.

In the particular case illustrated, the air jets 28 are located at each of the first six heating stations D, E, F, G, H and J, since the envelope" and flare are not actually united or sealed together until just after they begin to index away from station J. The jets of air 28 are directed downwardly into the open upper end of the envelope 9 by nozzles 29 and 29 overlying the upper envelope ends. The air pressure necessary for producing the downdraft through the envelope 2 may be conveniently determined by spacing the lower end of the envelope from the flare II a distance somewhat greater (such as A; inch or so) than any gap that is apt to ever occur between the said parts during the normal operation of the machine, and then adjusting the pressure of the air for the jets 28 so as to produce a slight outflow of air through the gap between the so spaced flare and envelope.

Where the machine is operated with every other head 2 loaded with lamp envelopes 9, the upper ends of which have just been sealed, it is then necessary to take precautions against cracking of the finished but still warm seal by the air jets 28. This may be done by preheating the air used for the air jets 28, in which case the jets may operate continuously. Preferably, however, an arrangement is provided for operating each air jet 28 only during those intervals when envelopes having unsealed upper ends are located at the corresponding station. For this purpose, one group of alternate nozzles 29 (Fig. 1) is connected to one manifold 30 while the other group of alternate nozzles 29 is connected to another manifold 30. The two manifolds 30, 30' are each connected to separate air lines 3i and 3|, respectively, each of which has a plunger valve 32 or 32 and an air heater or drier 33 connected therein. The air valves 32, 32' are supported from the machine bed in a position adjacent the periphery of the turret I, and are operated by spring-closed bell-crank levers 34 and 34' which are pivotally mounted on the housing portions 35 and 35' of the said valves. One arm of each of the valve operating levers 34, 34 extends to a point closely adjacent the periphery of the turret l and is provided with a roller 36 (or 36) adapted to be engaged by outwardly projecting cam lugs 3! extending from the periphery of the turret at equally spaced points therearound. The engagement of the rollers 36, 36 by the cam lugs 31 pivots the levers 34, 34' and thus causes their other arms to push in the plungers 38, 38 of the valves 32, 32 and so open the latter. As shown in Fig. 1, there is one cam lug 37 for every other head 2 on the turret l, and the air valves 32, 32 controlled by the lugs 37 are so spaced apart around the periphery of the turret as to be alternately actuated and maintained open by the lugs 31 during the entire interval when the turret remains stationary.

The envelopes 9 having the unsealed or open upper ends are loaded into those alternate heads 2 which correspond to the cam lugs 37, while the envelopes with the already sealed upper ends are loaded into the other alternate heads. When the alternate heads 2 carrying the envelopes with unsealed upper ends are positioned at stations D, F and H, then the air valve 32 is opened by the engagement of one of the cam lugs 31 with the roller 36' on the operating lever 34' for the said valve. Such opening of the valve 32' thus produces the air jets 28 from the nozz es 29 at the said stations D, F and H. Meanwhile, the air valve 32 controlling the nozzles 29 at the other stations E, G and J remains closed so that no air is directed from the nozzles 29 down onto the warm seal at the upper end of the envelopes located at said stations. When the turret subsequently indexes to its next position wherein the unsealed envelopes are located at stations E, G and J and already sealed envelopes are located at stations D, F and H, then the valve 32 controlling the air jets 28 at stations D, F and H is closed while the other valve 32 controlling the air jets 28 at stations E, G and J is opened. This alternate operation of the valves 32 and 32' then continues with each index of the turret so that the air jets 28 are on only when an envelope with an unsealed upper end is located therebeneath.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In the gas fire method of sealing a mount to the lower extremity of a vertically disposed tubular envelope open at both ends and internally coated with fluorescent material, the step of producing a downward flow of air through the envelope concurrently with substantially the entire period of heating of the envelope and mount by the gas fires prior to the complete interfusion thereof, to thereby prevent the water vapor in the gas heating fires from entering between the mount and envelope and passing upwardly through the envelope.

2. In the gas fire method of sealing a mount to the lower extremity of a vertically disposed tubular envelope open at both ends and internally coated with fluorescent material, the step of introducing air under pressure into the open upper end of the envelope concurrently with substantially the entire period of heating of the envelope and mount by the gas fires prior to the complete interfusion thereof, to thereby create an outward flow of air through any space existing between the mount and the envelope.

3. A sealing-in machine of the class described comprising the combination of a carrier having a plurality of heads for supporting a tubular envelope and a mount in sealing relation with the envelope upright and the mount at the lower end of the envelope, means for indexing said carrier, gas burners located at a series of heating stations occupied by the heads on said carrier and arranged to heat the lower ends of the envelopes and the adjacent portions of the mounts in said heads, and downwardly directed air nozzles located at said heating stations above and in alignment withthe path of travel of said heads so as to be in registry with the upper ends of envelopes in the heads at said heating stations and direct a stream of air downwardly into said envelopes whereby to at least neutralize any upward flow of gas or vapor through said envelope, a conduit connecting the nozzles at alternate stations with a source of compressed air, a second conduit connecting the nozzles at the intervening stations with said source of compressed air, a valve in each of said conduits having control means extending adjacent the path of travel of said carrier, and cam means on said carrier arranged to engage each of said valve control means alternately upon indexing of said carrier.

RAYMOND H. STUART.

' REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 355,714 Reinmann Jan. 11, 1887 2,023,628 Van Sant Dec. 10, 1935 2,143,696 Holmes et al. Jan. 10, 1939 2,212,842 McGowen Aug. 27, 1940 2,273,439 Freeman Feb. 17, 1942 2,336,874 Louden et al. Dec. 14, 1943 2,361,517 White et al Oct. 31, 1944 2,415,867 Cartun Feb. 18, 1947 2,417,361 Herzog Mar. 11, 1947 2,434,664 Malloy Jan. 20, 1948 

